Earlier quoted context omitted.
Which is odd when you realize that WebKit is older than the firefox engine. (WebKit is a direct descendant of khtml, Firefox was busing re-writing their Gecko engine when WebKit forked)
How much of a rewrite was it? IIRC they fixed a lot of bloat issues and called it a rewrite, but it wasn't a full rewrite.
I think the lack of embedding has hurt Gecko showing up in more projects. Their solution was XULRunner which inverts the model by embedding your app in Gecko instead of the other way around, and they don't even support that anymore.
I'm hoping GeckoView takes off on Android and makes its way back to desktop, but I'm afraid that will happen too late for people to care about it anymore.